Flat panel displays, or FPD's, are becoming increasingly more popular as an alternative to monitors utilizing conventional cathode ray tube (CRT) technology. FPD's, such as liquid crystal or active matrix displays, have inherent compactness advantages over CRT's because of their electronic nature. This advantage is readily apparent when noting the relative sizes between a personal computer monitor and a laptop computer display screen.
To satisfy the increasing demand for FPD's, manufacturers have sought to improve manufacturing efficiencies in production and, most notably, in the quality control area. Quality control often refers to the inspection, testing, or verification of one or more parameters of a device. Of significant importance for quality control purposes relating to FPD's are accurate measurements of the photometric and colorimetric properties of light generated by the displays under test. One of the keys to verifying the operability of FPD's is to employ instruments capable of detecting emitted radiation that corresponds as closely as possible with what an average human observer would experience.
Initial attempts at inspecting FPD's utilized conventional CRT inspection and measurement systems. Typically, these systems employed a photometer disposed in confronting relationship to the CRT for detecting one or more parameters of the light emitted by the display, such as luminance, contrast and chromaticity. To position the photometer at different orientations relative to the display, the system included a three-axis table having respective stages moveable along a Cartesian coordinate system. During test, the display remained fixed in an immobile position as the instrumentation followed an inspection path, or footprint.
While the conventional CRT inspection system described above worked well for its originally intended uses, as flat panel display technology improved, those skilled in the art recognized that measurements of the displays at orientations not normal to the display surface were not being considered in the verification criteria. This is primarily explainable because of the physics involved in the operation of CRT's which allows viewing of the screen from an angle with little effects on the light intensity sensed from particular pixels. Unlike CRT's, visible radiation emitted from FPD's drops off in intensity when viewed from the side, or at angles to the flat surface. This is because FPD's employ polarizing optics that cause the visible radiation emitted to drop off in intensity when viewed from the side, or at angles to the flat panel surface.
To account for angular flat panel display measurements, those skilled in the art proposed a relatively large and cumbersome five-axis inspection system. This system included the features of the three-axis CRT inspection system, but employed two additional rotary axes to pivot the instrumentation about two additional axes. With the rotational capability, the inspection equipment could orient the photometer in angular relationship to the display.
While the conventional five-axis system is believed capable of delivering inspection results at fairly acceptable rates of speed, the cumbersome construction of the system is believed capable of significant improvement. The conventional system described above typically has problems testing a range of FPD sizes due to the limited flexibility of the 5-axis positioning mechanism. For FPD testing, it is often important to have the capability of varying the distance between the instrumentation and the DUT quickly. Moreover, thorough FPD testing often involves exposing the DUT to a variety of environmental conditions in a sealed chamber. Conventional systems lack these capabilities.
Thus, the need exists for a multi-axis flat panel display system and method capable of providing measurements at relatively high throughput rates while maintaining a high level of flexibility. Moreover, the need exists for an inspection system having a unique footprint to allow open architectures for integrating into a variety of testing environments. The system and method of the present invention satisfy these needs.